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More on the digital fuel gauge.


Glenn Ashmore

Jan 1, 1970
You guys helped so well on my LED fuel gauges that I got a bit over
enthusiastic on my fuel management system so I am back looking for opinions
on an extention of the project.

I have decided to add a totalizer display and automatic shut down to the
transfer pump. I have a flow transducer that puts out 2,700 pulses per
gallon. I am going to feed it into a 4020 binary counter. Then I will use
one side of a 4082 to AND the 2, 4, 8 and 256 pins to get a pulse every 270
inpit pulses for one tenth of a gallon and feed that to an array of three
cascaded 4026s to drive a 3 digit 7-segment LED display. That part looks
like it is going to work so I pushed a little further.

I want to be able to pre-select how many gallons will be transfered. I
figure another 4020 ANDed the same way as the totalizer through the other
side of the 4082 but feeding a 40110 up/down counter driver . The counter
could be incremented by a pair of up/down buttons and a 555 timer. The
up/down buttons would also disable the totalizer driver and enable the set
driver so the same LED display could be used for both. That has to happen
on the first push of an up/down button and stay latched until a transfer
button is pressed. (I haven't figured that out yet.)

When a source tank's transfer start button is pressed: 1) a flipflop SET
goes high, 2) both 4020s are reset, 3) the totalizer driver is reset and
enabled while 4) the set driver is disabled and set in DOWN mode. 5) The
pump relay is activated and the flow transducer then feeds both 2020s which
feed their respective drivers.

The system remains in that stat until the shut down circuit goes high.
When the BORROW pin of the most significant 40110 set driver goes high
indicating the requested number of gallons have been transferred and the
system shuts down the pump relay. As a back up, the shut down circuit would
be tied to Q10 of the day tank level meter to trigger a shut down if it
fills before the request is completed and through inverting gates to the
Q2s of the supply tank meters to trigger a shutdown if it is empty.

OK, there is the theory. Somebody shoot it down before I log onto Digikey.
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at:
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